<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        window.onload=function(){
           function clock(){
                //1.获取画布
            var canvas=document.getElementById('canvas');
            //2.获取画笔
            var cx=canvas.getContext('2d');
            //3.设置画笔样式
            cx.fillStyle='green';
            cx.strokeStyle='black';
            //4.绘制图形
            //绘制表盘
            cx.beginPath();
            cx.arc(250,250,200,0,Math.PI*2);
            cx.closePath();
            cx.fill();
            //绘制时刻度
            cx.lineWidth=2;
           for(var i=0;i<12;i++){
            cx.save();
            cx.translate(250,250);
            cx.rotate(i*Math.PI/6);//先旋转再绘制
            cx.beginPath()
            cx.moveTo(0,-180);
            cx.lineTo(0,-200);
            cx.closePath();
            cx.stroke();  
            cx.restore();

            cx.fillStyle='black';
            cx.font='16px bold';
            cx.save();
            cx.translate(250,250);
            cx.rotate(i*Math.PI/6);
            cx.rotate(Math.PI/6);
            cx.fillText(i+1,-5,-220);
            cx.restore();
            
           }
           //绘制分刻度
           for(var i=0;i<60;i++){
            cx.save();
            cx.translate(250,250);
            cx.rotate(i*Math.PI/30);//先旋转再绘制
            cx.beginPath()
            cx.moveTo(0,-190);
            cx.lineTo(0,-200);
            cx.closePath();
            cx.stroke();
            cx.restore();
           }
           //绘制时针
           var today=new Date();
           var hour=today.getHours();
           var min=today.getMinutes();
           var sec=today.getSeconds();
           hour=hour+min/60;//eg:3.5小时
           cx.lineWidth=5;
           cx.save();
           cx.strokeStyle='black';
           cx.translate(250,250);
           cx.rotate(hour*Math.PI/6)
           cx.beginPath()
           cx.moveTo(0,-130);
           cx.lineTo(0,8);
           cx.closePath();
           cx.stroke();
           cx.restore();
           //绘制分针
           cx.lineWidth=3;
           cx.save();
           cx.strokeStyle='black';
           cx.translate(250,250);
           cx.rotate(min*(Math.PI/30))
           cx.beginPath()
           cx.moveTo(0,-150);
           cx.lineTo(0,8);
           cx.closePath();
           cx.stroke();
           cx.restore();
           //绘制秒针
           cx.lineWidth=1;
           cx.save();
           cx.strokeStyle='red';
           cx.translate(250,250);
           cx.rotate(sec*(Math.PI/30))
           cx.beginPath()
           cx.moveTo(0,-170);
           cx.lineTo(0,8);
           cx.closePath();
           cx.stroke();
           cx.restore();
           //绘制交界处
           cx.fillStyle='white';
           cx.save();
           cx.translate(250,250);
           cx.beginPath();
           cx.arc(0,0,5,0,Math.PI*2)
           cx.closePath();
           cx.fill();
           cx.lineWidth=2;
           cx.strokeStyle='red';
           cx.stroke();
           cx.restore();

           setTimeout(clock,1000);
           }
           clock()

            

        }
       
    </script>
</head>
<body>
    <canvas id="canvas" width="600px" height="600px" style="background-color: #ccc;"></canvas>
</body>
</html>